Image capture devices, such as digital video cameras or digital still cameras, are used in different applications and environments. An image capture device should be capable of producing high quality imagery under a variety of lighting conditions. For example, image capture devices should be capable of operating effectively in environments that include large amounts of reflected or saturated light, as well as in environments that include high levels of contrast. A typical image capture device performs automatic exposure to select an exposure value (EV) that achieves a certain target brightness for a scene. For example, an image capture device may select an EV that produces an image frame of the scene with an average brightness value equivalent to approximately 18% gray.
An automatic exposure process may adjust aperture size and shutter speed of the image capture device to correspond to the selected EV. In this way, the automatic exposure process controls an amount of light that reaches a sensor array within the image capture device to produce an image frame of a scene at the target brightness. However, some scenes may require a higher average brightness value while other scenes may require a lower average brightness value. For example, a snow scene includes a large amount of reflected light, for which the automatic exposure process may overcompensate, causing the image frame to look unnaturally dark. On the other hand, a scene containing a white document next to a black laptop includes a high contrast level, for which the automatic exposure process may also overcompensate, causing the white document to appear totally saturated in the image frame.
Exposure compensation is common in digital still cameras, but may also be utilized in digital video camera and other types of image capture devices. When the automatic exposure process does not provide the appropriate brightness for a scene, a user of the image capture device may perform exposure compensation by manually adjusting the EV selected by the automatic exposure process for the scene. The user may adjust the EV by manually setting the aperture size and shutter speed of the image capture device to let more or less light reach the sensor array within the image capture device to produce an appropriate brightness for the scene.